Fatigue Testing of Ring-Stiffened Traffic Signal Structures: FHWA-WY-08/05F
Based upon in-service inspection of pole with traditional designs, Wyoming DOT’s inventory exhibited approximately a one-third cracking rate. A ring-stiffened connection is presently used. Sixteen fatigue tests were performed on twelve ring-stiffened cantilevered traffic signal pole connections to quantify the fatigue resistance. Two poles sizes were tested in three loading configurations: in-plane, out-of-plane, and diagonal. Cyclic loading was applied to produce stress ranges at several levels and up to 16 ksi in the main member, more than six times the stress range observed during monitoring an in-service pole.
The WYDOT ring-stiffened connection appears to be adequate to resist Wyoming’s sustained winds that average approximate 12 mph in many locations. The possibility of using this connection with longer mast arms exists. Connection bolt fatigue failures were observed and may be the limiting fatigue design feature and important for inspection.